Field of Invention
The present invention relates to a polymer electrolyte fuel cell.
Discussion of Background
As a polymer electrolyte fuel cell, e.g. a specific polymer electrolyte fuel cell is known which has a membrane/electrode assembly having a cathode catalyst layer and a gas diffusion layer provided on one surface of a polymer electrolyte membrane in this order, and an anode catalyst layer and a gas diffusion layer provided on the other surface in this order; and separators disposed on both sides of the membrane/electrode assembly. The gas diffusion layer performs a function to diffuse air or fuel gas in the electrode and a function to discharge water formed in the electrode.
As a separator, a non-porous separator (e.g. a metal separator or a carbon separator) having a plurality of gas flow paths formed, has been widely used. However, in the case of a polymer electrolyte fuel cell using the non-porous separator, supply of gas tends to be non-uniform between a portion in contact with the gas flow paths of the separator and a portion not in contact with the gas flow paths, in the gas diffusion layer. As a result, in such a polymer electrolyte fuel cell, supply of gas to a cathode catalyst layer and an anode catalyst layer tends to be non-uniform, whereby a high cell voltage is hardly obtained.
Accordingly, it has been proposed to use a porous separator for a polymer electrolyte fuel cell in which gas can be uniformly supplied to a cathode catalyst layer and an anode catalyst layer with which a higher cell voltage can be obtained. For example, the following polymer electrolyte fuel cells (i) and (ii) are mentioned.
(i) A polymer electrolyte fuel cell comprising a membrane/electrode assembly having a gas diffusion layer, a cathode catalyst layer, a polymer electrolyte membrane, an anode catalyst layer and a gas diffusion layer disposed in this order, and current collector layers (separators) made of a gas permeable metal porous product disposed on both sides of the membrane/electrode assembly (Patent Document 1).
(ii) A polymer electrolyte fuel cell comprising a membrane/electrode assembly having a gas diffusion layer, a cathode catalyst layer, a polymer electrolyte membrane, an anode catalyst layer and a gas diffusion layer disposed in this order, and separators of which a portion in contact with the membrane/electrode assembly is formed from a sintered porous product made of a metal powder, disposed on both sides of the membrane/electrode assembly (Non-Patent Document 1).